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CROR Engine debris Middle level Impact and Mechanical test

Periodic Reporting for period 3 - ELEMENT (CROR Engine debris Middle level Impact and Mechanical test)

Reporting period: 2019-09-01 to 2021-02-28

The European Union (EU) aeronautic industry is a world leader in its sector, and contributes to the EU economy with more than 500000 jobs and with a turnover of close to 140 B€. The objective of the Clean Sky 2 program is to build a platform to potentiate the innovation in this important industry for the EU.

Fuel consumption is probably the most important factor in the civil aircraft industry, and almost all the innovations are focused in this subject, always without compromising the security. Lower fuel consumption not only means lower operating cost of the airlines, but also lower CO2 emissions.

One of the most promising technologies that could allow achieving the aforementioned goal is the Counter Rotatory Open Rotor (CROR) engine, which could offer an improvement in fuel consumption in the range of 15% - 20% compared to the actual engines. In order to use these new engines, the aircraft structure should be tolerant to its failure. In particular, the topic of this project is focused in blade release or an Uncontained Engine Rotor Failure (UERF); under these circumstances high energy debris could impact to the fuselage, causing large structural damages that could compromise the aircraft structure safety. The current proposal is focused in the development and maturation of innovative shielding solutions to sustain high and low energy debris associated with the engine failure.

There are two overarching objectives in this project. The first one is to validate the maturity level of different technologies and structural solutions, to protect the rear-end structure from different impacts associated to engine failure. To this end both real and virtual impact tests of debris associated with the engine failure will be performed on both simple panels and full-scale representative aircraft structures. The second objective of this project is to advance in the development of virtual testing methodologies.
The main objective of this project is to validate the maturity level of different technologies and structural solutions, to protect the rear-end structure of a civil aircraft from different impacts associated to engine failure. The project defines two steps in approaching to this problem. The first one (level 1) considers small flat panels in order to compare different shielding solutions, whereas in the second one (level 2) full scale aircraft structures will be contemplated in order to validate the shielding solutions selected in level 1 phase.

The first part of the work has focused in preparing the experimental set-up for the experimental level 1 tests (L1). In order to perform the experimental tests, a pneumatic launcher was used. In total more than 300 tests have been performed for the L1. The experimental study has covered metals, composites, and other combinations of materials. At the same time numerical simulations have been performed to analyse the best boundary conditions for the shielding considered. Finally, in order to understand the behaviour of the tested nets, a material characterization of the different yarns have been performed.

The second part of the project was focuosed of structures more representatives of an aircraft; these included in some of the cases curvature, stringers and frames. In total around 30 impact tests have been performed of this level. In addition, a numerical methodology has been developed to perform virtual test of high velocity impacts of metallic fragments in different types of structures, both made using composites and metals. Variables such as the impact location, the impact velocity the friction… etc have been considered in order to analyse its influence in the structure behaviour.

As an overview of the results and their exploitation and dissemination, it is possible to say that this project was very important for both the Universidad Carlos III de Madrid (UC3M) and for the company Vazquez y Torres Ingeniería S.L. (VTI). The UC3M will dramatically increase its capacity of performing high velocity impact tests with the new launcher that will be one of the largest ones along Europe. This upgrade will help to increase the workload of the laboratory since the Lightweight Structures Dynamic Group could apply to other projects and also start new collaborations with other companies thanks to the better facilities. By the other hand, VTI will add the development of a large experimental launcher devices to its capacities, which could later be used for other projects, increasing its portfolio of products. This company will increase its competitiveness in the field of experimental setups developed for the aeronautic and aerospace industries. The UC3M has presented some of the results in different conferences and workshops and it will present the rest of the achievements in future meetings. It will also publish some article in specialized journals.
The CROR engines seem to be the best option in order to increase the fuel efficiency and the economics of the commercial civil aircraft for low and medium range. The use of this engine presents many challenges to the engineers, because of its position in the rear-end, which will promote many modifications regarding the different systems. One of the main objectives of this project is to validate the maturity level of different shielding solutions to protect the rear-end against the impact of both blades and debris in case of engine rotor failure. Once validated, the path to adopt these new engines will be much clearer, since the protection of the fuselage is one of the key factors. It is possible to state then that the impact of the conclusions of this project are very important and also will have important consequences on the rest of the program to adopt the CROR engines. The knowledge in protections and shielding could lead in the development of more competitive structures and hence aircraft.

Another important objective of this project is to develop a virtual testing methodology to predict the behaviour of complex structures. Numerical models are usually validated with experiments performed on small specimens. Sometimes this validation could not be easily extrapolated to large structures such aeronautics ones; a representative aeronautic structure includes metallic frames, composite stringers and metallic joints between the different elements. In this project the numerical methodology has been validated with both simple specimens and complex structures (L1 and L2 tests). This tool will positively impact on the economics of the future developments for the Airbus Company, since the number of tests for other high velocity impact analysis will be considerably reduced. These kinds of advances are key to increase the competitiveness of the European aeronautic sector. One of the most relevant impacts of this project is related to one of the most important problems of the Spanish society, which is the unemployment and in particular the one related to high qualified positions. A project like the current will allow to increase the competitiveness of the local industry thanks to the activities developed, which could help other transport industries and increase the number of skilled jobs.

Finally, the University Carlos III de Madrid has been positively impacted since thanks to the ELEMENT project, it has starting research activities in other fields such as the high-speed rail. In this new project the effect of the impact of ballast on the train structure is investigated.
Square barrel developed to launch L2 metallic fragments
Simulation of high velocity impact on CFRP structure
L2 structure to be tested